Fluorescence microscope study of the binding of added C protein to skeletal muscle myofibrils.
The binding of extra C protein to rabbit skeletal muscle myofibrils has been investigated by fluorescence microscopy with fluorescein-labeled C protein or unmodified C protein plus fluorescein-labeled anti-C protein. Added C protein binds strongly to the I bands, which is consistent with its binding to F actin in solution (Moos, C., C. M. Mason, J. M. Besterman, I. M. Feng, and J. H. Dubin. 1978. J. Mol. Biol. 124:571-586). Of particular interest, the binding to the I band is calcium regulated: it requires a free calcium ion concentration comparable to that which activates the myofibrillar ATPase. This increases the likelihood that C protein-actin interaction might be physiologically significant. When I band binding is suppressed, binding in the A band becomes evident. It appears to occur particularly near the M line, and possibly at the edges of the A band as well, suggesting that those parts of the thick filaments that lack C protein in vivo may nevertheless be capable of binding added C protein.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002352:Carrier Proteins; D004533:Egtazic Acid / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009124:Muscle Proteins / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism* / Q000648:ultrastructure; D011817:Rabbits; D000099163:Myosin Binding Protein C
D002118:Calcium; D002352:Carrier Proteins; D004533:Egtazic Acid; D009124:Muscle Proteins; D000099163:Myosin Binding Protein C